This invention relates to design analysis of components and, more particularly, to a method, system and computer program product that provide for automated design analysis of components and the component interconnect structure by subjecting a finite element model of the component to various simulated thermo-mechanical environments and enabling modification of the component design and interconnect structure if the component""s stress response to the environmental load is outside of pre-selected limits.
Components that are attached to an overall structure, such as an aircraft, automobile, bridge, etc. are subjected to various forces and temperatures over the lifetime of the overall structure. The components may be any type of board or panel-type structures with parts and/or electronic elements mounted thereupon, including printed wiring assemblies, printed wiring boards, chassis containing printed wiring assemblies or boards, transducers, and multifunctional parts with embedded electronics. Typically, the parts and/or electronic elements are attached in some way to the board or panel-type structure, such as by solder or solder balls, which is called the interconnect structure of the component. The forces and temperatures create stresses in the component that can eventually cause wear, damage, and the possible failure of the component interconnect structure, which may adversely affect the operation of the overall structure containing the component. As such, design analysis of the components is important to ensure that a component design does not cause it to have a shorter fatigue life than desired. Design analysis provides component and structural designers with critical information used to determine the likelihood and the causes of fatigue-related failures. Once the component and structural designers have the results of the design analysis, they can design the individual components and the overall structure so as to withstand the anticipated stress and temperature levels over the design lifetime.
The conventional method of design analysis involves initially designing a component using the processes and materials that have been shown, through testing or experience, to create the most durable and effective component. This design may be evaluated using military standards, such as the MIL Handbook 217 for electronics, and if it meets the standards, then a component having this design is built. The component design is tested by subjecting the component to accelerated stresses that are representative of forces or temperatures experienced by the component and the overall structure containing the component. The testing for each type of force and temperature must be performed separately and in separate chambers that simulate the desired testing environment. The testing environments may include, for instance, a thermal testing environment, a vibration testing environment, an acoustic testing environment, and a shock testing environment.
For example, if acoustic testing of the component is desired, then the component must have the exact type of boundary conditions that it will have in operation, i.e., the component must be mounted to the segment of the overall structure that will carry the component with the type of fasteners that will be used in operation. To acoustically test the component, the component and segment of the overall structure are placed in an acoustic chamber where the sonic load spectrum of the acoustic pressures at a typical operating environment are duplicated. The fluctuating acoustic pressure creates vibration base-excitement that acts upon the component. The response of the component is monitored and recorded to determine which parts of the component interconnect structure fail due to the vibration and when they fail, i.e. the failure mode. If the response of the component indicates that an integral part, such as an electronic element, of the component will fail prematurely, then the component interconnect structure must be redesigned to try to mitigate the effect of the vibration on the electronic element at issue. The redesign process may include moving the electronic element to a different portion of the board that is more resilient to vibration, changing the type of material that is used to make the electronic element to a material that is more resilient to vibration, and/or changing the type of material, such as solder, used to attach the electronic element to the board or panel-type structure, in addition to many other ways that the component may be redesigned. The redesigned component is then re-tested using the process described above and this cycle continues until the component design can withstand the acoustic test without any part of the component interconnect structure failing. Typically, it takes two to three cycles of design/redesign and testing before the component design is optimized.
The design/redesign and testing process is similar for the other testing environments and if a subsequent environmental test leads to another redesign of the component, then the component interconnect structure must be re-tested in the prior environment to monitor the response of the further redesigned component in the prior environment. The testing and re-testing continues in the desired environments until the component design is optimized for all of the environments.
Thus, the design/redesign and testing process is a very time consuming and expensive endeavor because of the multiple redesign and testing cycles that may be involved in obtaining an optimal component design and interconnect structure for all of the desired testing environments. In addition, because the testing in the environmental chamber consists of applying accelerated environmental loads to the component, it is not an accurate simulation of the environmental loads that the component will actually experience over the lifetime of the component or the overall structure. As such, accelerated testing generally induces failure mechanisms in the interconnect structure of the component that are different than those experienced by the component in application, which may create misleading failure results and lead to inaccurate redesigns. Furthermore, the military standards that may be used to evaluate the initial design of some components are too broad to assist in determining the impact of detail design changes on the fatigue life of a component. That is, the standards are not helpful for evaluating the design of components in which small design changes may greatly affect the fatigue life of the component interconnect structure in relation to a certain environment because the military standards do not approach the level of detail required for such an evaluation.
Therefore, the conventional design analysis procedure does not accurately identify potential failure points of a component interconnect structure that are associated with the design, manufacture and operation of the component. In addition, the conventional design analysis procedure is extremely expensive and time consuming. As such, there exists a need in the industry for a component design analysis that accurately and efficiently simulates thermo-mechanical environments for testing the component interconnect structure and identifies potential failures within the component interconnect structure when subjected to the environment(s). The need is also for a design analysis that predicts the fatigue life for the component or the part of the component interconnect structure that fails and pinpoints the cause of the failure in order to identify the part or other aspect of the component interconnect structure that must change.
The method, system and computer program product of the present invention provides design analysis of a component that accurately and efficiently simulates thermo-mechanical environments for testing the component and identifies potential failures within the component interconnect structure when subjected to the environment(s). In addition, the method, system and computer program product of the present invention accurately identify potential failure points of a component interconnect structure that are associated with the design, manufacture and operation of the component. As such, the fatigue life for the component and/or any part of the component interconnect structure may be predicted and the exact cause of the failure may be pinpointed in order to identify the aspect of the component interconnect structure that must change.
The method, system and computer program product for design analysis of a component of the present invention include generating a finite element model of the component and receiving user-defined parameters that define a plurality of variables associated with the component. The plurality of variables that are received include at least one thermo-mechanical environment parameter. The thermo-mechanical environment parameter may be a thermal environment parameter, an acoustic environment parameter, a vibration environment parameter, and/or a shock environment parameter. The user-defined variables associated with the component that are received may also include at least one manufacturing parameter for the component, such as the type of solder used in the component, and at least one boundary condition for the component, such as the type of fasteners used to mount the component to the structure.
The method, system and computer program product of one embodiment of the present invention may also receive finite element properties and information regarding at least one part of the component. The information regarding at least one part of the component maybe received from a database of parts information following a definition of the part(s) by a user. The system of the present invention includes a client element for receiving the information described above and a processing element that is responsive to the client element and that also performs the functions described hereinbelow, unless otherwise specified.
The method, system and computer program product for design analysis of a component also subject the finite element model of the component to at least one environmental load and determine the stress response of the finite element model based upon the environmental load(s). The environmental load may be a thermal environmental load, an acoustic environmental load, a vibration environmental load, and/or a shock environmental load.
One advantageous embodiment of the method, system and computer program product of the present invention involves subjecting the finite element model of the component to at least one environmental load by subjecting the finite element model of the component to a computational first load and a computational second load. The maximum stress responses of the finite element model of the component to the computational first load and second load may be determined and a ratio constructed, which is a conversion factor for linking the two types of loads. This embodiment also may involve obtaining a first environmental load to test against the component and applying the ratio to the first environmental load in order to convert the first environmental load to represent an equivalent a second environmental load. The finite element model of the component may then be subjected to the equivalent of the second environmental load. In this embodiment, the stress response of the finite element model may be determined based upon the second environmental load.
To subject the finite element model of the component to an acoustic environmental load in the embodiment described above, the finite element model of the component may be subjected to a 1 psi uniform acoustic pressure load, which is the first computational load, and a 1 g negative based vibration acceleration load, which is the second computational load. The maximum stress responses of the finite element model of the component to the loads are determined and a ratio constructed, which is a conversion factor between an acoustic pressure load and a vibration acceleration load for the component. Prior to determining the maximum responses, the boundary conditions may be defined and applied to the finite element model of the component. This embodiment may also include obtaining either an acoustic pressure load or a vibration acceleration load to test against the component. If an acoustic pressure load is obtained, then applying the ratio to it converts it to an acceleration load. Alternatively, if a vibration acceleration load is obtained, then applying the ratio to it converts it to an acoustic pressure load.
Another advantageous embodiment of the method, system and computer program product of the present invention involves subjecting the component to an acoustic environmental load by simulating a comparable vibration acceleration environment. This embodiment includes subjecting the finite element model to a computational acoustic load, which may be a 1 psi uniform acoustic pressure load. Boundary conditions are applied to the finite element model and a maximum pressure response of the finite element model to the acoustic environmental load and boundary conditions is determined. The maximum pressure response is also based upon a selected sonic pressure load for testing against the component that is converted to a pressure power spectral density according to conventional techniques. The finite element model of the component is also subjected to a computational vibration acceleration load, which may be a 1 g negative based vibration acceleration load. The Boundary conditions are also applied to the finite element model and a maximum vibration acceleration response of the finite element model to the vibration acceleration environmental load and boundary conditions is determined. The maximum vibration acceleration response is also based upon the selected sonic pressure load for testing against the component that is converted to a pressure power spectral density according to conventional techniques. The maximum vibration acceleration response is determined by assuming the acceleration power spectral density is equal to the pressure power spectral density. The maximum pressure response and the maximum vibration acceleration response are placed in a ratio, which is a conversion factor for linking an acoustic environment to a vibration environment for the component. The ratio is then applied to the pressure power spectral density to convert it to an equivalent vibration acceleration power spectral density, and an input for a shaker table is generated according to the vibration acceleration spectral density. The component is secured to the shaker table, the vibration input is applied to the shaker table, and the response of the component to the vibration input is monitored.
Thus, the method, system and computer program product of the present invention provide automated design analysis of a component based upon user-defined parameters that include at least one thermo-mechanical environment parameter against which to test the component. A finite element model of the component is utilized, such that most, if not all, of the environmental testing may be computer generated via finite element analysis, which greatly decreases the expense and time involved in environmental testing. In addition, the finite element model of the component may be easily modified by altering the user-defined parameters of the component, such as the design and other features of the component, and regenerating the finite element model based upon the modified parameters. This is a significant advantage over the conventional design analysis process of redesigning and rebuilding the component after each environmental test, if necessary. Therefore, the method, system and computer program product of the present invention permit a structural or component designer to test prototype component designs without the expensive environmental chambers that are necessary in the conventional design analysis process. In addition, the components may be subjected to different testing environments simultaneously, which greatly decreases the time and expense of design analysis as compared to the conventional design analysis process in which the prototype component is subjected to each testing environment separately, particularly if the component must be redesigned and re-tested.
Furthermore, the method, system and computer program product of the present invention may subject the component to a type of environmental load that is time-consuming and expensive to generate, such as an acoustic load, the maximum stress responses of the component to a computational load of that environment and a computational load of an environment that is less time-consuming and less expensive to generate, such as a vibration environment. When the magnitude of the acoustic environmental load for which component testing is desired is known, it may be multiplied by the ratio to obtain the corresponding magnitude of the vibration environmental load. The vibration environmental load then may be applied to the component via a shaker table to obtain a component stress response that corresponds to the component stress response to the associated acoustic environmental load. Thus, the method, system and computer program product of the present invention provide an efficient process for subjecting a component to an acoustic environmental load by utilizing a corresponding vibration environment load.
The method, system and computer program product of the present invention further include determining whether the stress response is within pre-selected limits. If the stress response is outside of the pre-selected limits, then the method, system and computer program product of the present invention prompt modification of the design of the component and/or the user-defined parameters and regenerate the finite element model for the component. The method, system and computer program product of the present invention may also store the finite element model as a representation of the design of the component if the stress response is within the pre-selected limits. The system of the present invention may therefore include a storage element to store the finite element model as described above.
In one embodiment of the method, system and computer program product of the present invention, the stress response of the finite element model may be converted to a fatigue life for the component. The fatigue life may then be compared to a target fatigue life, which is a pre-selected limit for the component, to determine whether the stress response of the component is within the pre-selected limits. For this embodiment, if the fatigue life for the component is shorter than the target fatigue life for the component, then prompting modification of the design of the component and/or at least one user-defined parameter includes determining whether the component design and/or at least one user-defined parameter causes the fatigue life for the component to be shorter than the target life for the component.
Thus, the method, system and computer program product of the present invention provide analysis of the component""s stress responses to the environmental loads by comparing the component""s stress responses with pre-selected limits. The method, system and computer program product may also compute a fatigue life for the component or a part of the interconnect structure of the component based upon the stress responses to the environmental loads and compare it to a target fatigue life for the component. In addition, the method, system and computer program product identify the part(s) of the interconnect structure of the component that responded outside of the pre-selected limits, identify the type of environmental load that caused the part of the interconnect structure of the component to respond the way it did, prompt the user to modify the component design or other user-defined feature of the component at issue, and regenerate the finite element model of the modified component for further testing. Therefore, the method, system and computer program product of the present invention provide a complete analysis to the user that permits the user to immediately and appropriately modify the correct portion of the component, such that the user does not have to employ the trial and error procedure of the conventional design analysis to identify the reason that the component or portion of the component failed during testing.
Other embodiments of the method, system and computer program product of the present invention may also include creating a drawing of a design of the component prior to generating the finite element model of the component. The drawing may include creating a three dimensional computer aided drawing of the component design. In addition, the drawing of the component design may be a drawing of the design of the electronics imbedded in the component.
The method, system and computer program product for design analysis of a component of the present invention are therefore advantageous over the conventional design analysis techniques because they efficiently subject a finite element model of the component to the appropriate thermo-mechanical environment(s) for testing the component, evaluate the component""s stress response to the environmental loads, and compare the stress response to pre-selected limits. In addition, the method, system and computer program product of the present invention accurately identify potential failure points of the component that are associated with the design, manufacture, and operation of the component, identify the type of environmental load that caused the failure, prompt the user to modify the design or other user-defined parameter of the component at issue, and further test a finite model of the modified component. Thus, the method, system and computer program product of the present invention provide an economical and timely design analysis for components that enables users to efficiently determine the appropriate design for the components based upon the type of thermo-mechanical environments to which the component will be subjected over its lifetime.